1. Field of the Invention
The subject invention is generally related to cylindrical lock and key sets and is specifically directed to a cylindrical lock and key set having an electrical interlock which is disabled when the cylinder is forcibly removed.
2. Description of the Prior Art
The subject invention is related to the co-pending application entitled "ANTI-TAMPERING MAGNET FOR AUTOMOBILE IGNITION LOCK", Ser. No. 07/607,583, filed on Nov. 1, 1990 by D. Janssen and assigned to the assignee herein.
Over the last several years, it has become increasingly desirable to improve the anti-tampering feature of lock and key sets. This is particularly true with respect to automobile ignition systems where auto theft has almost developed into an art form. Skilled thieves can often "hot wire" an automobile ignition in a manner of a few seconds. Typically, the key and cylinder lock for engaging and energizing the ignition system is either bypassed or pulled in order to facilitate the theft. To combat this, automotive manufacturers have incorporated a variety of vehicle anti-tampering systems (VATS) to make vehicle theft more difficult. Numerous of these include electrical or electronic interlocks working in cooperation with a mechanical lock system. For example, one such system includes a resistor element on the mechanical key and a circuit connection contained within the bezel or knob of the cylinder of the key lock. When a mated key with the proper resistance level is inserted in the cylinder, the circuit is closed and the proper coded voltage is produced, permitting the ignition to energize in typical fashion when the cylinder is rotated. If a key with an improper resistance level is used, the proper voltage is not produced and the rotation of the cylinder will not enable the ignition system.
In another example, a sensor is placed at a certain point in the rotation of the cylinder and senses proper rotation of the cylinder to produce an ignition activation signal. Any attempt to start the ignition without first properly rotating the cylinder is ineffective since proper rotation is required to generate the ignition activation signal. There are instances where the cylinders have been forcibly pulled from the sleeve and modified to override the electronic interlock and then reinserted to activate the ignition. Prior art devices have not successfully dealt with this problem.
While the need for VATS ignitions in automobiles has created the development of the electronic interlock technology, it will be readily apparent that there are a wide variety of uses for which the interlock systems can be incorporated. The electronic interlock systems for the vehicle ignition circuits are readily adaptable to any lock and key set utilizing a key with a rotating cylinder lock.